Image of the week: a collision at 2,760,000,000,000 eV

Smashing together lead nuclei at 2.76 TeV might be fun and provide us with some nice pictures, but it has a strong scientific purpose.

It’s to create and understand a state of matter known as the quark-gluon plasma. This ‘quark soup’ consists of free quarks and gluons, and gives physicists a unique opportunity to study quantum chromodynamics. In our image this week, we’re looking at the way the initial conditions of this soup affect the observed physics, and it turns out they are pretty important.

Comparison between (a) a typical fluctuating event and (b) a smooth initial entropy density profile of hydrodynamical evolution of 2.76 TeV central Pb–Pb collisions.

Comparison between (a) a typical fluctuating event and (b) a smooth initial entropy density profile of hydrodynamical evolution of 2.76 TeV central Pb–Pb collisions.

It’s complex stuff though, with a large number of initial parameters affecting how the quark-gluon plasma behaves. Our image of the week looks at just one aspect of this – check out the paper for the details. Here’s what the author’s have to say on the image:

In figure 5, we compare the initial entropy density distribution in the transverse plane from a typical fluctuating event (figure 5(a)) and a smooth one generated by averaging over 100 000 fluctuating initial profiles for 0%–7.5% Pb–Pb collisions at 2.76 TeV at the LHC (figure 5(b)). We note that in figure 5(b), the initial profiles of all the events have been rotated to the same second-order participant plane before performing the event average of the entropy density. One can clearly see the presence of hot and cold regions in the QGP fireball for fluctuating initial conditions.

I’m glad we cleared that up.

Read more:

Paper: The influence of initial state fluctuations on heavy quark energy loss in relativistic heavy-ion collisions [this work]

Focus issue: 40 years of collective flow in relativistic heavy ion collisions—the barometer for primordial hot and dense QCD matter

Review: Initial state fluctuations and final state correlations in relativistic heavy-ion collisions

Review: Anisotropic hydrodynamics for ultra-relativistic heavy-ion collisions


CC-BY logoThis work is licensed under a Creative Commons Attribution 3.0 Unported License

Image: From Shanshan Cao et al 2015 J. Phys. G: Nucl. Part. Phys. 42 125104, Copyright IOP Publishing Ltd 2015.



Categories: Journal of Physics G: Nuclear and Particle Physics, JPhys+

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